Pneumatically actuated switching device with ball contact means

ABSTRACT

An electrically conductive sleeve having a bore therethrough is connected to a first conductor that is adapted to be connected to one side of an electrical circuit. A second conductor is mounted in an opening in the sleeve and is adapted to be connected to the other side of the electrical circuit. An electrically conductive ball is mounted in the bore and is movable by applying pneumatic pressure thereto betwen a circuit open position out of electrical communication with the second conductor and a circuit closed position in electrical communication with the second conductor and the sleeve. A cam surface extends into the bore and cams the ball into electrical communication with the second conductor and the sleeve in the circuit closed position. In a preferred embodiment, the cam surface is defined by a spring which flexes as the ball moves into and out of the circuit closed position so that the surface of the ball wipes against the surfaces of the bore and the spring, to clean such surfaces and thereby promote effective electrical communication therebetween. The bore is carefully dimensioned to very close tolerances so that the device is responsive to the application of a minimum pneumatic pressure. The pneumatic pressure is supplied by a deformable bulb manufactured in one piece by an injection molding technique to preclude leakage.

United States Patent [191 Dwyer I PNEUMATICALLY ACTUATED SWITCHINGDEVICE WITH BAlLlL CONTACT MEANS [76] Inventor: Philip W. ll wyer, PO,Box 51182,

Jacksonville Beach, Fla. 32250 22 Filed: Dec. 27, 1972 21 Appl. No.:318,735

[52] US. Cl..... 2011/81 11, 200/164 R, ZOO/DIG. 29, 200/166 BE, 60/533[51] Int. Cl. 1101111 35/241 [58] ll ieltl of Search. 200/81 11, 83 Z,82 R, 164 R, ZOO/DIG. 29, 86 A, 166 BE, 166 BF, 166

B11, 166 CT, 16 D, 61.52, 61.45 M; 222/206,

Primary Examiner-Robert K. Schaefer Assistant ExaminerGerald P. Tolin [57] ABSTRACT An electrically conductive sleeve having a bore therethroughis connected to a first conductor that is adapted to be connected to oneside of an electrical circuit. A second conductor is mounted in anopening in the sleeve and is adapted to be connected to the other sideof the electrical circuit. An electrically conductive ball is mounted inthe bore and is movable by applying pneumatic pressure thereto betwen acircuit open position out of electrical communication with the secondconductor and a circuit closed position in electrical communication withthe second conductor and the sleeve. A cam surface extends into the boreand cams the ballinto electrical communication with the second conductorand the sleeve in the circuit closed position. In a preferredembodiment, the cam su'rfaceis defined by a spring which flexes as theball moves into and out of the circuit closed position so that thesurface of the ball wipes against the surfaces of the bore and thespring, to clean such surfaces and thereby promote effective electricalcommunication therebetween. The bore is carefully dimensioned to veryclose tolerances so that the device is responsive to the application ofa minimum pneumatic pressure. The pneumatic pressure is supplied by adeformable bulb manufactured in one piece by an injection moldingtechnique to preclude leakage.

21 Claims, 8 Drawingllfigures PATENTEU JUL SHEET 1 OF 3 FIG.1

FATENTED L 9W 31.820285 SHEET 0F 3 COMPRESSED BACKGROUND OF THEINVENTION This invention relates generally to pneumatically operateddevices for switching electrical circuits, and is particularly wellsuited for use in environments where it is undesirable to use aconventional electrical switch, such as in atmospheres containing a highconcentration of potentially explosive gas. A good example of such anenvironment is in hospital rooms and the like, where oxygen commonly isused. Also, since the device is operated by only slight pressure on anactuating bulb, it is well suited for use by geriatric and otherpatients in a weakened or disabled condition. However, use of theinvention is not limited to hospitals and like institutions, although adescription of the invention as used in such an institution facilitatesan understanding thereof Hospitals and like institutions usually have asignalling system by which each patient may signal a central station,such as a nurses station, to summon assistance. Such systems arenormally electrical in nature, and frequently each patient is providedwith a conventional electrical switch which opens and closes a signalcircurt.

Under certain situations, notably when oxygen is being used, electricalswitches cannot be utilized in close proximity to the patient because ofthe possibility of arcing within the switch, which could cause ignitionof combustibles in an atmosphere containing a high concentration ofoxygen, with catastrophic results. Therefore, there have been developeda number of switching devices for opening or closing a signal circuit bypneumatic means. While this basic theory is sound, the prior artpneumatically actuated switching devices have not been entirelysatisfactory. For example, a patient in a weakened or disabled conditionmust be able to operate the device, and thus the device should beresponsive to the application of a minimum pneumatic pressure. Also, thedevice must operate reliably over long periods of time withoutmaintenance, often in an atmosphere that is deleterious to thecomponents thereof.

SUMMARY OF THE INVENTION It is the object of this invention to providean improved pneumatically actuated switching device that is extremelyresponsive and reliable.

The pneumatically actuated switching device of the invention comprisesan electrically conductive sleeve having a bore therethrough. Anelectrically conductive ball is mounted in the bore and is movable inresponse to the application of pneumatic pressure thereto. A porous airfilter is mounted adjacent one end of the bore to allow the passage oflow pressure air in and out of the bore to facilitate movement of theball, and to prevent dust and dirt from gaining entrance into the bore.The other end of the bore is in communication with a tube to which isconnected a source of pneumatic pres sure, such as a deformable bulb.

The device includes two conductors respectively adapted to be connectedto two sides of an electrical circuit, such as a signal circuit. Thefirst conductor is in electrical communication with the sleeve. Thesecond conductor is mounted in an opening in the sleeve which extendsinto the bore. The ball is movable between a circuit open position outof electrical communication with the second conductor, and a circuitclosed position in electrical communication with the second conductorand the sleeve. A cam surface extends into the bore and into the path ofthe ball, and cams the ball into electrical communication with thesecond conductor and the sleeve in the circuit closed position. Thesleeve normally is oriented generally vertically, although the deviceoperates satisfactorily when the sleeve is oriented almost horizontallybecause the ball moves in the bore with very little, if any, friction.The ball can be positioned above the cam surface, wherein the circuitnormally is closed and the ball is moved to open the circuit, or belowthe cam surface, wherein the circuit is normally open and the ball ismoved to close the circuit.

In a preferred embodiment, the cam surface is defined by a spring havinga leg which flexes during movement of the ball to and from the circuitclosed position, so that during the last portion of travel of the balltoward the circuit closed position and the first portion of travel ofthe ball away from the circuit closed position, the surface of the ballwipes against the surfaces of the bore and the spring, cleaning suchsurfaces upon each actuation of the device. Such wiping precludes thedeposition of foreign matter on the surfaces which may tend to cause theball to stick and adversely affect the sensitivity of the device.Particularly, such wiping prevents the deposition of sulfides on thesurfaces which would adversely affect the conducting properties of thesurfaces and cause arcing. Since the conductive surfaces usually areplated, arcing is particularly harmful,

because it can erode the plating away entirely. The

spring also cushions and thereby minimizes bouncing of the ball as theball moves into the circuit closed positioned, thus fostering a smooth,precise switching action.

In a preferred embodiment, the second conductor also extends into thebore and arrests the movement of the ball in the circuit closedposition. The cam surface may be defined by the second conductor or aspring attached to the-second conductor.

Significantly, while the device responds to the appli cation of a verysmall amount of pressure on the deformable bulb, it is not easilyactuated by quick, sharp blows to the bulb, such as would be appliedwhen the bulb is dropped. This is because actuation of the devicerequires displacement of a certain minimum volume of air from the bulb,which volume is not displaced by quick, sharp blows to the bulb.

The basic principles of this invention are applicable to electricalcircuits in which only a momentary opening or closing of the switchingdevice is necessary, as well as circuits in which opening or closing ofthe switching device must be maintained until the device is reset. Inthe latter instance, a locking means, such as a magnet, locks the ballin the position to which it is moved pneumatically. The device is resetby means, such as a plunger, for releasing the ball from the lockingmeans and moving it back to the normal position.

The clearance between the ball and the surface of the bore in any of theembodiments of the invention must be extremely small in order to providea device that is sensitive to the application of a minimum of pneumaticpressure. Proper dimensioning of the bore is difficult, especially whenthe sleeve is placed, and a novel method of dimensioning the bore hasbeen developed. The bore is first reamed, and then is initially sized byballizing with a ball of hard material, such as tungsten carbide. Thediameter of the initial sizing ball is approximately equal to thedesired final diameter of the bore plus twice the thickness of theplating. The bore is then plated with an electrical conductive material,such as silver. The bore is then finally sized by ballizing with a ballof hard material having a diameter slightly greater than the desiredfinal diameter of the bore to compensate for slight elastic deformationof the plating during the final sizing.

The deformable bulb which is used to supply the pneumatic pressure foroperating the device must be leak-proof. Typically, the bulb consists ofa chamber and a neck. The chamber has a transverse cross-section that issubstantially wider than the transverse crosssection of the neck. Thebulb is best manufactured in one piece, and a new method of doing so hasbeen developed. The bulb is made in one piece by injection molding anelastometric material in a mold cavity defined between an outer mold andan inner mandrel. Im-

mediately after the injection molding, the bulb, with the mandrelremaining inside, is removed from the mold cavity. The bulb is thencooled to an elevated temperature below the temperature at which theelastomeric material acquires elastic memory. A pressurized fluid, suchas air, is then injected into the bulb through a passage in the mandrel,ejecting the bulb from the mandrel. During the ejection of the bulb fromthe mandrel, the neck stretches to accommodate the mandrel, but becausethe material has acquired elastic memory, the bulb returns to theoriginal molded shape.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a firstembodiment of the pneumatically actuated switching device of theinvention, with the ballin the circuit open position;

FIG. 2 is a sectional view of the device of FIG. 1, with the ball in thecircuit closed position;

FIG. 3 is a sectional view of a second embodiment of the pneumaticallyactuated switching device of the invention, with the ball in the circuitopen position;

FIG. 4 is a sectional view of the device of FIG. 3, with the ball at aposition intermediate the circuit open and circuit closed positions;

FIG. 5 is a sectional view of the device of FIG. 3, with the ball in thecircuit closed position;

FIG. 6 is a sectional view of a third embodiment of the pneumaticallyactuated switching device of the invention, with the ball in the circuitclosed position;

FIG. 7 is a perspective view of a pneumatically actuated switchingdevice of the invention to which a plurality of actuator bulbs areconnected; and

FIG. 8 is an elevational view, partially in section, showing ejection ofthe bulb from the mandrel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pneumatically actuatedswitching device of the invention can be used in a variety of systemsand environments in which it is desirable to switch an electricalcircuit on or off by remote means. The device is particularly wellsuited for use with conventional nurse call signal systems and, since inthis context the features of the invention are highlighted, theinvention is described herein in combination with such a system.However, it should be understood that the invention is not limited tosuch use.

The pneumatically actuated switching device of the invention comprisesfive basic components: a sleeve 10, a ball 11, a housing 12, anelectrical plug 13, and a pneumatic actuating means, such as a tube 14and a deformable bulb 15.

A first embodiment of the invention is shown in FIGS. 1 and 2. Sleeve 10is of cylindrical configuration and has a cylindrical bore 22 extendingtherethrough and a pair of open ends 20 and 21. An opening 23 isprovided in sleeve 10 intermediate ends 20 and 21 and extending intobore 22. This arrangement allows sleeve 10 to be utilized withoutmodification for both normally open circuit and normally closed circuitelectrical systems, as will be explained below. At least the portion ofthe'surface of bore 22 opposite opening 23 is electrically conductive,or sleeve 10 may be manufactured entirely of a conductive material, orsleeve 10, including the surface of bore 22, may be plated or otherwisecoated with a conductive material. To provide maximum sensitivity, amaterial having excellent conductivity, such as silver, should be used,and it is therefore economically expedient to manufacture sleeve 10 froma conductive material, such as brass, and then plate the sleeve,including the surface of bore 22, with silver. Alternatively, only anarrow annular band 24, shown in phantom in FIG. 1, adjacent opening 23,need be plated or otherwise formed from a conductive material.

Movably mounted in bore 22 is an electrically conductive ball 11.Similarly to sleeve 10, ball 11 may be manufactured entirely of aconductive material, or may be plated with such material. Again, toprovide maximum sensitivity, a material having excellent conductivity,such as silver, should be used. Ball 11 is movable in bore 22 inresponse to the application of pneumatic pressure thereto. It is quiteimportant that ball 11 be freely movable in bore 22, and it is equallyimportant that the clearance between the outer surface of the ball andthe surface of the bore be as small as possible, so that the ballfunctions as a piston in response to the applicationof a very smallamount of pneumatic pressure. The clearance between bore 22 and ball 11should be of the magnitude of 0.0015 inch or less. This necessitatesdimensioning bore 22 very accurately. A novel process for accomplishingsuch dimensioning is set forth below.

Sleeve 10 is mounted in a bore 25 of housing 12. The housing is madefrom a non-conductive material and includes a stem 26 at one endthereof. A passage 27 extends through 'stem 26 and communicates at theinterior end thereof with open end 21 of sleeve 10. The outer surface ofstem 26 is provided with a number of annular ridges 28. Stem 26 isinserted into the end of pneumatic tube 14. An annular collar 29, whichmay be made from an elastic material, in installed around tube 14 andcooperates with ridges 28 to clamp tube 14 securely to stem 26 in aleak-free connection. While this is a preferred manner of connectingtube 14 to housing 12, other means may be used, as long as theconnection is leak-free.

A porous air filter 16 is press-fit into bore 25 at the other end ofhousing 12. Filter 16 abuts open end 20 of sleeve 10 and allows lowpressure air to flow freely into and out of bore 22 while preventingdirt and moismm from entering the bore which could interfere with theproper operation of the device. Filter 16 can be made from any suitablematerial such as metal, refractory or plastic.

Housing 12 also is provided with a passage 30 communicating with opening23 and substantially perpendicularto bore 25. Plug 13 is mounted inpassage 30, and comprises an externally disposed tubular elementconductor 33 and an internally disposed rod element conductor 32.Conductors32 and 33 are'electrically insulated from one another byinsulation means 34. A

conductive cap 35 is connected to the outer end of con-' ductor 32. Plug13 fits into a conventional receptacle (not shown) in the conventionalmanner. Within the receptacle, external conductor 33 is connected to oneside of a signal circuit, and internal conductor 32 is connected to theother side of such circuit via cap 35.

Internal conductor 32 may be a conventional machine screw and terminatesat the inner end thereof in a hemispherical head 37. Head 37 extendsthrough opening 23 into bore 22 and into the path of ball 11, but isspaced from the edges of opening 23 so that there is no directelectrical communication between head 37 and sleeve 10. If desired,insulating material may be placed in the space between head 37 and theedges of opening 23. Head 37 is provided with a cam surface 38, whichmay be the surface of the head. Cam surface 38 preferably is plated witha material having excellent conductivity, such as silver. Cam surface 38is inclined in such a manner to cam ball 11 into positive contact withthe surface of bore 22 and the cam surface, and thereby insure goodelectrical communication therebetween in the circuit closed position ofthe ball. This arrangement also compensates for any looseness in fitbetween ball 11 and bore 22 because the ball is, in a sense, arrested byhead 37 in a wedge-like action.

External conductor 33 is in electrical communication with sleeve via aconductive pin 40 that is inserted through a small bore 11 in housing 12contiguous with conductor 33. Pin 40 is received in a recess 42 insleeve 111. However, if only the surface of bore 22 is platedorotherwise formed from a conductive material, pin 40 must communicatedirectly with the surface of the bore.

The responsiveness of the device is enhanced by the particular shape ofbulb 13. As illustrated in FIGS. 3 and 7, bulb 13 has a chamber 103which includes opposed sides 1211; such sides being substantiallyflattened, slightly convex and of generally circular configuration.Sides 120 have a relatively large surface area and define the majorportion of the surface area of chamber 103. Thus, slight compressivedeformation of one or both of sides .120 causes a substantial volumetricchamber in chamber 105, thereby displacing a relatively largevolume ofair from within the chamber. This advantage is not achieved with bulbsof other shapes, especially those of round cross-section employed inmany prior art devices. Bulb 13 also includes a neck 1% and is connectedto tube 14 by a connector 1117.

The operation of this embodiment is as follows: Plug 13 is inserted intothe receptacle of an electrical system, such as a nurse call signalsystem. While it is desirable that sleeve 10 be substantially verticallyoriented, the device will operate properly with the sleeve inclined onlytwo degrees from the horizontal. In practice, the weight of tube 14tends to orient housing 12, and thus sleeve 10, substantiallyvertically. In FIGS. 1 and 2 the device is illustrated in the context ofa system in which the circuit normally is open; a signal being initiatedby closing the circuit. In such a system. ball 11 is positioned in thelower portion of bore 22, and normally rests against the bottom of bore23. To close the electrical circuit, conductors 32 and 33 must be placedin electrical communication with one another. This is accomplished bymoving ball 11 upwardly from the normal circuit open position shown inFIG. 1 to the circuit closed position shown in FIG. 2. To move ball 11upwardly, the user squeezes bulb 15, forcing air through tube 14 andpassage 27. Due to the close tolerance between ball 11 and bore 22, theball reacts as a piston, and moves upwardly in the bore to the positionshown in FIG. 2. In this position, ball 11 contacts cam surface 38 andis arrested in a wedge-like action between cam surface 38 and bore 22.This arrangement promotes effective electrical communication between thesurfaces of ball 11, bore 22 and cam surface 38.

. In the circuit closed position shown in FIG. 2, ball 11 is inelectrical communication with conductor 32 via head 37, and withconductor 33 via pin 40 and sleeve 10. Therefore, the electrical circuitis closed. Upon relaxation of the pneumatic pressure in the system, ball11 will drop or roll to the lower portion of bore 22, thus again openingthe circuit. In the usual signal system, only a momentary closing (oropening) of the circuit is sufficient to initiate the desired signal,which will be maintained until reset from a central-station,notwithstanding the subsequent opening (or closing) of the switchingdevice.

I The second preferred embodiment of the invention is shown in FIGS. 3-3and in many respects is identical to the embodiment previouslydescribed. However, the second embodiment incorporates an additionalnovel feature which provides a number of additional advantages.

In the second embodiment of the invention, internal conductor 32terminates at the inner end thereo in a hemispherical head 30. Agenerally U-shaped leaf spring 31 made from a'copper alloy is attachedto head 30. Spring 31 has a contact leg 32 and a mounting leg 33, suchlegs being connected by a hinge portion 34. While spring 31 can beattached to head 30 in a number of manners, there is a preferred manner,as follows: Head 311 is provided with a slot, indicated generally at 33.The base of slot 33 is defined by a first inclined portion 36 and asecond inclined portion 37. Mounting leg 33 is attached to base portion36 by conventional means, such as by soldering, so that hinge portion341 will not be coated with solder, which would detrimentally affect thetlexure characteristics of spring 31.

Head extends into bore 22 and into the path of ball 11 so that themovement of ball 11 is arrested by the head. However, contact leg 32extends slightly inwardly beyond head 51) and has the free end thereoforiented in the direction of the circuit open position of ball 11. Suchfree end defines a cam surface 33 which preferably is plated withsilver. Cam surface 38 engages ball 11 during movement of the ball intoand out of the circuit closed position. During such engagement, spring31 flexes and contact leg 32 moves inwardly and outwardly of slot 33.Thus, the circuit can actually be closed upon contact between ball 11and cam surface -7 58 slightly before and after the ball is in thecircuit closed position.

The operation of the embodiment shown in FIGS. 3-5 is described in thecontext of a system in which the signal circuit normally is closed, andis opened to initiate a signal. In FIG. 3, ball 11 is shown in the upperportion of bore 22, where it has been moved by the application ofpneumatic pressure thereto by bulb 15 through tube 14. In FIG. 3, theelectrical circuit is open. Upon release of the pneumatic pressure ball11, under the action of gravity and the suction of bulb 15, dropsdownwardly to the position shown in FIG. 4, which is the moment of firstcontact between the ball and cam surface 58. Under optimum conditions,the electrical circuit will close at this moment. Ball 11 continuesthrough the position shown inFlG. 4, however, causing contact leg 52 toflex inwardly, finally being arrested by head 50 in the circuit closedposition shown in FIG. 5. During the movement of ball 11 between theposition shown in FIG. 4 to that shown in FIG. 5, and vica versa, camsurface 58 engages ball 11 and cams the ball into contact with thesurface of bore 22. Thus, the surface of ball is pressed into intimatewiping contact with the surfaces of bore 22 and cam surface 58. This isa key feature of the invention, and eliminates some heretofore unsolvedproblems of the prior art devices. Wiping of the various surfacesagainst one another cleans the surfaces and prevents the deposition ofsulfides or other contaminants thereon which would deteriously affectthe conducting properties of the surfaces and result in arcing. Arcingwould quickly erode the surfaces, particularly plated surfaces, therebydestroying the sensitivity and reliability of thedevice. For example,when silver plated surfaces are wiped clean, a pneumatic pressure ofonly about two inches of water is required to raise ball 11 from thecircuit closed position shown in FIG. 5 to the circuit open positionshown in FIG. 3. but if the silver plating is eroded away, a

pneumatic pressure of as much as about twelve inchesof water isrequired, because ball 11 tends to stick in the circuit closed position.The extent to which contact leg 52 extendsbeyond head 50 is kept to aminimum, commensurate with the desired wiping of the surface of ball 11against the surfaces of bore 22 and cam surface 58.

While spring 51 has been shown as U-shaped, other spring configurationsmay be employed, within the limitation of providing a biased cam surfaceto interact with the ball in the novel manner described above,

It should be noted that in both of the embodiments described above, theposition of the ball can be reversed so that the circuit is actuated inthe manner opposite to that described. In such instance, the camsurface, either on head 37 or on spring 51, is reoriented to engage andcam ball 11 in the desired manner.

The above two embodiments illustrate the invention for use with circuitswhere a momentary opening (or closing) of the circuit is sufficient toinitiate and maintain the signal. However, in some signal circuits, thesignal will be maintained only as long as the circuit is switched open(or closed). In this type of circuit, the ball must be held in theposition to which it is moved, and returned to its normal position byreset means.

The third embodiment of the invention shown in FIG. 6 embodies such astructure. As in the previously described embodiments, a sleeve 10having a bore 22 therethrough is mounted in a housing 12. A conductiveball 11 made from a magnetically susceptible material is movably mountedin bore 22. A plug 13 having an external conductor 33 and an internalconductor 13 is mounted in a bore 30 in housing 12. Internal conductor32 terminates at the inner end thereof in a hemispherical head 50 whichhas a slot 55 therein, as described above. In this embodiment, head 50does not extend through opening 23 into bore 22 and into the path ofball 11. However, a spring 51 is attached to head 50, as describedabove, with the contact leg 52 thereof extending into bore 22 and intothe path of ball 11.

A reset assembly, including a porous air filter, is mounted in bore 25at the end of housing 12 opposite stem 26. Also, a locking means,comprising a cylindrical magnet 70, is mounted in bore 25 at the sameend of housing 12. Magnet has a diameter less than the diameter of bore25 and is inserted into such bore against open end 20 of sleeve 10. Anannular air passage 71 is defined between the outer periphery of magnet-70 and the inner surface of bore 25. Magnet 70 has a dished recess 73for engaging ball 11, an axial bore 76 therethrough, and a transverseair passage 74 communicating between bore 76 and air passage 71. Whenball 11 moves upwardly into engagement with recess 73, the air above theball flows into bore 76 and through passages 74 and 71 upwardly aroundmagnet 70. Mounted on the outer end of magnet 70 is an insulator disc77, having an opening 78 therein. A porous air filter 80 is press-fitinto bore 25 against disc 77. Filter 80 has a first axial bore 81partially therethrough and a second axial bore 82 having a diameter lessthan the diameter of bore 81 through the remainder thereof. An insulatedsleeve 84 having a flange 85 extends through bores 81, 82, opening 78and into bore 76, and aligns magnet 70 and insulator disc 77 coaxiallyof filter 80 and bore 25.

A reset plunger 87 having a head 88 extends through sleeve 84. An O-ring89 and a locking ring 90 seal plunger in sleeve 84. A return spring 92is coiled about plunger 87 and acts against locking ring 90 and head 88.A non-conductive cap screw 94 having a head of greater diameter thanplunger 87 is screwed into the end of the plunger and engages the end ofsleeve 84 to properly position the plunger.

The operation of this embodiment is as follows: In response to pneumaticpressure applied by squeezing bulb 15, ball 11 begins to move upwardlyfrom the position shown in phantom in FIG. 5. The pneumatic pressureneed move ball 11 only into the magnetic field of magnet 70. When theball is in such field, it is drawn upwardly toward magnet 70 until it isengaged in recess 73, as shown in solid lines in FIG. 6. Ball 11 is thuslocked in position by magnet 70. At a point slightly in advance of thelocked position, ball 11 contacts cam surface 58 which cams the ballinto contact with the surface of bore 22 so that the surface of the ballwipes against the surfaces of the bore and cam surface, as describedabove. The movement of ball 11, however, is not arrested by head 50. Theelectrical circuit is closed through spring 51. Ball 11 remains engagedin recess 73 until reset plunger 87 is manually depressed sufficientlyto move the ball out of the magnetic field of magnet 70.

Since ball 11 and sleeve 10 are in the electrical circuit while the ballis in recess 73, magnet 70 also becomes charged. However, magnet 70 isinsulated from filter 80 and reset plunger 87 by disc 77, sleeve 84 andscrew 94 so that no external elements of the device hecome charged. Ifdesired, reset plunger 87 also may be made from a non-conductivematerial.

Several alternative arrangements of the components of the deviceillustrated in FIG. 6 are possible. While the device is shown for usewith a normally open circuit system, the device is equally suitable foruse with a normally closed circuit system, in which instance opening 23would be positioned in the lower portion of sleeve 10. Thus, spring 51would normally engage ball ll 1, and upward movement of the ball towardmagnet 70 would open the circuit.

The pneumatically actuated switching device of the invention may beoperated from several stations. As shown in H6. '7, a pair of bulbs 15aand 151) may be connected in parallel to a common tube 14 by means of amanifold dd. The device will then be operated by squeezing either bulb.

In view of the close fit required between ball ill and the surface ofbore 22, the bore must be dimensioned in a very precise manner. This isparticularly difficult when sleeve T is plated with a conductivematerial, such as silver, because the plating operation by nature is notaccurate. A particularly efficient method has been developed fordimensioning the bore to the exacting measurements required.

A plurality of balls llll are manufactured, including plating, by knowntechniques. The balls will have'slight variations in diameter, and areseparated by diameter into lots. This allows the bore of the sleeveassociated with a particular ball to be very accurately dimensioned. Thebore is first reamed to roughly establish the dimension thereof, and isthen initially sized by ballizing with a ball of hard material, such astungsten carbide. The diameter of the initial sizing ball isapproximately equal to the desired final diameter of the bore, plustwice the desired thickness of the plating.

Bore 22 is then plated, usually by plating the entire sleeve. Thethickness of the plating on the surface of the bore is about 0.0005inch. The plating material usually is silver, but may be anotherconductive material. The bore is then finally sized by ballizing with aball of hard material having a diameter slightly greater than thedesired final diameter to compensate for slight elastic deformation ofthe plating during the final sizing.

The manufacture of the pneumatic squeeze bulb also poses some specialproblems. The bulb must have no leaks and should not have a propensityfor developing leaks during use. It istherefore advantageous tomanufacture chamber 1105 and neck 1106 in one piece, and a new methodfor doing so has been discovered.

The transverse cross-section of chamber T is substantially wider thanthe transverse cross-section of neck 1106. Bulb is manufactured fromvinyl or a similar elastomeric material by an injection molding processin a mold cavity formed between an outer mold (not shown) and an innermandrel 110. Mandrel 110 comprises a chamber forming portion ill and aneck forming portion 112. Mandrel 110 further comprises an injection gaspassage H3 communicating at one end with a source of pressurized fluid,such as air (not shown) and at the outer end with the interior of a bulb15 formed thereon. A check valve 11115 is installed in passage M3 sothat the elastomeric material will not enter passage M3 when thematerial is injected into the mold cavity. The outer mold is of the typethat can be opened to remove the mandrel from the mold cavity.

First, the elastomeric material in a high temperature, liquid state isinjected under pressure into the mold cavity in a conventional manner,and changer 1105 and neck 106 are formed to the desired size and shapeon mandrel llltl. Then, while the material is still at an elevatedtemperature, mandrel 110, with the formed bulb thereon, is removed fromthe mold cavity. The bulb is then allowed to cool to an elevatedtemperature below the temperature at which the elastomeric materialacquires elastic memory. A jet of high pressure fluid is then injectedvia passage 113 into the interior of the bulb, ejecting the bulb frommandrel ll1l0. Neck 106 must stretch to the width of chamber formingportion llll during this ejection, as shown'in FIG. 8, but it has beenfound that such stretching is accomplished without damage, and the bulbquickly returns to its molded shape.

It is to be understood that while specific preferred embodiments of theinvention are herein illustrated and described, and the invention hasbeen disclosed for use with a particular type of electrical system, theinvention is not to be limited to such embodiments or for use with suchsystems, but is defined solely by the scope of the appended claims.

I claim:

1. A pneumatically actuated switching device comprising:

a sleeve having a cylindrical bore extending therethrough and an openingtherein extending into said bore, at least the portion of the surface ofsaid bore opposite said opening being electrically conductive;

a first electrical conductor means in electrical communication with saidconductive portion and adapted to be connected to a first side of anelectrical circuit;

a second electrical conductor means mounted in said opening and adaptedto be connected to a second side of said electrical circuit;

an electrically conductive ball movably mounted in said bore, said ballbeing movable between a circuit open position out of electricalcommunication with said second electrical conductor means and a circuitclosed position in electrical communication with said second electricalconductor means and said conductive portion, whereby said the ball is insaid circuit closed position said first and second electrical conductormeans are placed in electrical communication with one another, said ballnormally being in one of said positions;

a cam surface attached to said second electrical conductor means andextending into said bore and into the path of movement of said balladjacent said circuit closed position for camming said ball intoelectrical communication with said second electrical conductor means andsaid conductive portion, said cam surface comprising an electricallyconductive generally U-shaped spring having a contact leg and a mountingleg, said legs being connected by a hinge portion, said contact legextending into said bore and said mounting leg being attached to saidsecond electrical conductor means with said hinge portion free fromcontact with said second electrical conductor means, whereby flexing ofsaid spring is unimpaired, said contact leg extending pneumaticactuating means connected to said sleeve and communicating with one endof said bore, said actuating means being selectively operable to movesaid ball from said one position to the other of said positions byapplying pneumatic pressure thereto.

2. A pneumatically actuated switching device comprising:

a sleeve having a cylindrical bore extending therethrough and an openingtherein extending into said bore, at least the portion of the surface ofsaid bore opposite said opening being electrically conductive;

a first electrical conductor means in electrical communication with saidconductive portion and adapted to be connected to a first side of anelectrical circuit; I

a second electrical conductor means mounted in said opening and adaptedto be connected to a second side of said electrical circuit; 7

an electrically conductive ball movably mounted in said bore, said ballbeing movable between a circuit open position out of electricalcommunication with said second electricalconductor means and a circuitclosed position in electrical communication with said second electricalconductor means and said conductive portion, whereby when the ball is insaid circuit closed position said first and second electrical conductormeans are placed in electrical communication with one another, said balln0rmally-being in one of said positions;

a cam surface extending into said bore and into the path of movement ofsaid ball adjacent said circuit closed position for camming said ballinto electrical communication with said second electrical conductormeans and said conductive portion;

pneumatic actuating means connected to said sleeve for communicatingwith one end of said bore, said actuating means being selectivelyoperable to move said ball from said one position to the other of saidpositions by applying pneumatic pressure thereto;

prising: f

a sleeve having a cylindrical bore extending therethrough and an openingtherein extending into said bore, at least the portion of the surface ofsaid bore opposite said opening being electrically conductive;

a first electrical conductor means in electrical communication with saidconductive portion and adapted to be connected to a first side of anelectrical circuit;

a second electrical conductor means mounted in said opening and adaptedto be connected to a second side of said electrical circuit;

an electrically conductive ball movably mounted in said bore, said ballbeing movable between a circuit open position out of electricalcommunication with said second electrical conductor means and a circuitclosed position in electrical communication with said second electricalconductor means and said conductive portion, whereby when the ball is insaid circuit closed position said first and second electrical conductormeans are placed in electrical communication with one another, said ballnormally being in one of said positions;

an electrically conductive spring means in electrical communication withone of said conductors and positioned in said bore substantiallyopposite the other of said conductors, said spring means protruding intothe path of movement of said ball at said circuit closed position andextending therefrom toward said circuit open position to intercept saidball in advance of said circuit closed position, said ball therebyflexing said spring so that the surface of said ball wipes against thesurface of said bore and said spring means during the final portion ofmovement into said circuit closed position and the initial portion ofmovement out of said circuit closed position to thereby clean saidsurfaces and thus promote effective electrical communicationtherebetween; and

pneumatic actuating means connected to said sleeve and communicatingwith one end of said bore, said actuating means being selectivelyoperable to move said ball from said one position to the other of saidpositions by applying pneumatic pressure thereto.

4. The pneumatically actuated switching device of claim 3, wherein saidsleeveis oriented at an angle to the horizontal and said pneumaticactuating means communicates with the lower end of said bore, said ballbeing mounted in the portion of said bore extending above said springmeans and being normally in said circuit closed position, said pneumaticactuating means moving said ball to said circuit open position.

5. The pneumatically actuated switching device of claim 3, wherein saidsleeve is oriented at an angle to the horizontal and said pneumaticactuating means communicates with the lower end of said bore, said ballbeing mounted in the portion of said bore extending below said springmeans and being normally in said circuit open position, said pneumaticactuating means moving said ball to said circuit closed position.

6. The pneumatically actuated switching device of claim 3, furthercomprising air filter means mounted adjacent the other end of said bore.

7. The pneumatically actuated switching device of claim 3, wherein saidspring means is attached to said second electrical conductor means.

8. 'The pneumatically actuated switching device of claim 7, wherein saidsecond electrical conductor means also extends into said bore and intothe path of movement of said ball and arrests the movement of the ballin said circuit closed position.

9. The pneumatically actuated switching device of claim 3, wherein saidspring means comprises a leaf spring having a leg extending into saidbore, said leg having a free end oriented in the direction of saidcircuit open position.

it'll-The pneumatically actuated switching device of claim 3, whereinsaid spring means comprises a generally U-shaped spring having a contactleg and a mounting leg, said legs being connected by a hinge portion,said contact leg extending into said bore and said mounting leg beingattached to said second electrical conductor means with said hingeportion free from contact with said second electrical conductor means,whereby flexing of said spring is unimpaired.

111. The pneumatically actuated switching device of claim 3, furthercomprising a housing and a plug means, said sleeve being mounted in saidhousing and said plug means being mounted in said housing in alignmentwith said opening, said plug means including an externally disposedtubular element comprising said first electrical conductor means and aninternally disposed rod element comprising said second electricalconductor means, said plug means being adapted to be received by areceptacle connected to said electrical circuit.

ill-The pneumatically actuated switching device of claim ll, whereinsaid pneumatic actuating means comprises a deformable bulb and a tube,one endof said tube being connected to said bulb and the other end ofsaid tube being connected to said housing adjacent said one end of saidbore, whereby when said plug means is received by a generally horizontalreceptacle the weight of said tube tends to orient said sleeve generallyvertically with said one end of said bore oriented downwardly.

13. The pneumatically actuated switching device of claim 3, wherein saidpneumatic actuating means comprises a deformable bulb and a tube, oneend of said tube being connected to said bulb and the other end of saidtube communicating with said one end of said bore.

14. The pneumatically actuated switching device of claim 3, wherein saidpneumatic actuating means comprises a manifold communicating with saidone end of said bore, and a plurality of deformable bulbs connected inparallel to-said manifold, whereby pneumatic pressure may be applied tosaid ball by any one of said bulbs.

15. The pneumatically actuated switching device of claim 3, furthercomprising means for locking said ball adjacent said other position, andreset means for releasing said ball from said locking means.

16. The pneumatically actuated switching device of claim 115, whereinsaid locking means comprises a magnet means mounted adjacent the otherend of said bore.

17. The pneumatically actuated switching device of claim 13, whereinsaid cam surface is defined by an electrically conductive spring meansattached to said second electrical conductor means.

13. The pneumatically actuated switching device of claim 15, whereinsaid reset means comprises a reset rod mounted substantially coaxiallyof said bore and movable into said bore through the other end thereof,said reset rod engaging said ball upon movement thereof into said bore,whereby movement of the reset rod into said bore releases the ball fromsaid locking means and moves the ball toward said one position.

19. The pneumatically actuated switching device of claim 18, whereinsaid locking means comprises a magnetic means mounted adjacent the otherend of said first-mentioned bore and having a second bore therethrough,said reset rod being movable through said second bore into said firstbore.

20. The pneumatically actuated switching device of claim 3, wherein saidpneumatic actuating means comprises a deformable bulb having a pair ofopposed,

slightly convex actuating sides of relatively large area.

circular configuration.

l= l= =i

1. A pneumatically actuated switching device comprising: a sleeve havinga cylindrical bore extending therethrough and an opening thereinextending into said bore, at least the portion of the surface of saidbore opposite said opening being electrically conductive; a firstelectrical conductor means in electrical communication with saidconductive portion and adapted to be connected to a first side of anelectrical circuit; a second electrical conductor means mounted in saidopening and adapted to be connected to a second side of said electricalcircuit; an electrically conductive ball movably mounted in said bore,said ball being movable between a circuit open position out ofelectrical communication with said second electrical conductor means anda circuit closed position in electrical communication with said secondelectrical conductor means and said conductive portion, whereby said theball is in said circuit closed position said first and second electricalconductor means are placed in electrical communication with one another,said ball normally being in one of said positions; a cam surfaceattached to said second electrical conductor means and extending intosaid bore and into the path of movement of said ball adjacent saidcircuit closed position for camming said ball into electricalcommunication with said second electrical conductor means and saidconductive portion, said cam surface comprising an electricallyconductive generally Ushaped spring having a contact leg and a mountingleg, said legs being connected by a hinge portion, said contact legExtending into said bore and said mounting leg being attached to saidsecond electrical conductor means with said hinge portion free fromcontact with said second electrical conductor means, whereby flexing ofsaid spring is unimpaired, said contact leg extending along said boretoward said circuit open position so that said contact leg engages saidball during movement of the ball to and from said circuit closedposition, said ball flexing said spring during movement of the ball toand from said circuit closed position, whereby the surface of said ballwipes against the surfaces of said bore and said spring during movementof the ball to and from said circuit closed position, to thereby cleansaid surfaces and thus promote effective electrical communicationtherebetween, and pneumatic actuating means connected to said sleeve andcommunicating with one end of said bore, said actuating means beingselectively operable to move said ball from said one position to theother of said positions by applying pneumatic pressure thereto.
 2. Apneumatically actuated switching device comprising: a sleeve having acylindrical bore extending therethrough and an opening therein extendinginto said bore, at least the portion of the surface of said boreopposite said opening being electrically conductive; a first electricalconductor means in electrical communication with said conductive portionand adapted to be connected to a first side of an electrical circuit; asecond electrical conductor means mounted in said opening and adapted tobe connected to a second side of said electrical circuit; anelectrically conductive ball movably mounted in said bore, said ballbeing movable between a circuit open position out of electricalcommunication with said second electrical conductor means and a circuitclosed position in electrical communication with said second electricalconductor means and said conductive portion, whereby when the ball is insaid circuit closed position said first and second electrical conductormeans are placed in electrical communication with one another, said ballnormally being in one of said positions; a cam surface extending intosaid bore and into the path of movement of said ball adjacent saidcircuit closed position for camming said ball into electricalcommunication with said second electrical conductor means and saidconductive portion; pneumatic actuating means connected to said sleevefor communicating with one end of said bore, said actuating means beingselectively operable to move said ball from said one position to theother of said positions by applying pneumatic pressure thereto; meansfor locking said ball adjacent said other position; and reset means forreleasing said ball from said locking means, said reset means comprisinga reset rod mounted substantially coaxially of said bore and movableinto said bore through the other end thereof, said reset rod engagingsaid ball upon movement thereof into said bore, whereby movement of thereset rod into said bore releases the ball from said locking means andmoves the ball toward said one position.
 3. A pneumatically actuatedswitching device comprising: a sleeve having a cylindrical boreextending therethrough and an opening therein extending into said bore,at least the portion of the surface of said bore opposite said openingbeing electrically conductive; a first electrical conductor means inelectrical communication with said conductive portion and adapted to beconnected to a first side of an electrical circuit; a second electricalconductor means mounted in said opening and adapted to be connected to asecond side of said electrical circuit; an electrically conductive ballmovably mounted in said bore, said ball being movable between a circuitopen position out of electrical communication with said secondelectrical conductor means and a circuit closed position in electricalcommunication with said second electrical conductor means and saidcOnductive portion, whereby when the ball is in said circuit closedposition said first and second electrical conductor means are placed inelectrical communication with one another, said ball normally being inone of said positions; an electrically conductive spring means inelectrical communication with one of said conductors and positioned insaid bore substantially opposite the other of said conductors, saidspring means protruding into the path of movement of said ball at saidcircuit closed position and extending therefrom toward said circuit openposition to intercept said ball in advance of said circuit closedposition, said ball thereby flexing said spring so that the surface ofsaid ball wipes against the surface of said bore and said spring meansduring the final portion of movement into said circuit closed positionand the initial portion of movement out of said circuit closed positionto thereby clean said surfaces and thus promote effective electricalcommunication therebetween; and pneumatic actuating means connected tosaid sleeve and communicating with one end of said bore, said actuatingmeans being selectively operable to move said ball from said oneposition to the other of said positions by applying pneumatic pressurethereto.
 4. The pneumatically actuated switching device of claim 3,wherein said sleeve is oriented at an angle to the horizontal and saidpneumatic actuating means communicates with the lower end of said bore,said ball being mounted in the portion of said bore extending above saidspring means and being normally in said circuit closed position, saidpneumatic actuating means moving said ball to said circuit openposition.
 5. The pneumatically actuated switching device of claim 3,wherein said sleeve is oriented at an angle to the horizontal and saidpneumatic actuating means communicates with the lower end of said bore,said ball being mounted in the portion of said bore extending below saidspring means and being normally in said circuit open position, saidpneumatic actuating means moving said ball to said circuit closedposition.
 6. The pneumatically actuated switching device of claim 3,further comprising air filter means mounted adjacent the other end ofsaid bore.
 7. The pneumatically actuated switching device of claim 3,wherein said spring means is attached to said second electricalconductor means.
 8. The pneumatically actuated switching device of claim7, wherein said second electrical conductor means also extends into saidbore and into the path of movement of said ball and arrests the movementof the ball in said circuit closed position.
 9. The pneumaticallyactuated switching device of claim 3, wherein said spring meanscomprises a leaf spring having a leg extending into said bore, said leghaving a free end oriented in the direction of said circuit openposition.
 10. The pneumatically actuated switching device of claim 3,wherein said spring means comprises a generally U-shaped spring having acontact leg and a mounting leg, said legs being connected by a hingeportion, said contact leg extending into said bore and said mounting legbeing attached to said second electrical conductor means with said hingeportion free from contact with said second electrical conductor means,whereby flexing of said spring is unimpaired.
 11. The pneumaticallyactuated switching device of claim 3, further comprising a housing and aplug means, said sleeve being mounted in said housing and said plugmeans being mounted in said housing in alignment with said opening, saidplug means including an externally disposed tubular element comprisingsaid first electrical conductor means and an internally disposed rodelement comprising said second electrical conductor means, said plugmeans being adapted to be received by a receptacle connected to saidelectrical circuit.
 12. The pneumatically actuated switching device ofclaim 11, wherein said pneumatic actuating means comprises a deformablebulb and a tube, One end of said tube being connected to said bulb andthe other end of said tube being connected to said housing adjacent saidone end of said bore, whereby when said plug means is received by agenerally horizontal receptacle the weight of said tube tends to orientsaid sleeve generally vertically with said one end of said bore orienteddownwardly.
 13. The pneumatically actuated switching device of claim 3,wherein said pneumatic actuating means comprises a deformable bulb and atube, one end of said tube being connected to said bulb and the otherend of said tube communicating with said one end of said bore.
 14. Thepneumatically actuated switching device of claim 3, wherein saidpneumatic actuating means comprises a manifold communicating with saidone end of said bore, and a plurality of deformable bulbs connected inparallel to said manifold, whereby pneumatic pressure may be applied tosaid ball by any one of said bulbs.
 15. The pneumatically actuatedswitching device of claim 3, further comprising means for locking saidball adjacent said other position, and reset means for releasing saidball from said locking means.
 16. The pneumatically actuated switchingdevice of claim 15, wherein said locking means comprises a magnet meansmounted adjacent the other end of said bore.
 17. The pneumaticallyactuated switching device of claim 13, wherein said cam surface isdefined by an electrically conductive spring means attached to saidsecond electrical conductor means.
 18. The pneumatically actuatedswitching device of claim 15, wherein said reset means comprises a resetrod mounted substantially coaxially of said bore and movable into saidbore through the other end thereof, said reset rod engaging said ballupon movement thereof into said bore, whereby movement of the reset rodinto said bore releases the ball from said locking means and moves theball toward said one position.
 19. The pneumatically actuated switchingdevice of claim 18, wherein said locking means comprises a magneticmeans mounted adjacent the other end of said first-mentioned bore andhaving a second bore therethrough, said reset rod being movable throughsaid second bore into said first bore.
 20. The pneumatically actuatedswitching device of claim 3, wherein said pneumatic actuating meanscomprises a deformable bulb having a pair of opposed, slightly convexactuating sides of relatively large area.
 21. The pneumatically actuatedswitching device of claim 20, wherein said actuating sides are ofgenerally circular configuration.